DMPA, an injectable depot formulation of medroxyprogesterone (MPA), is a commonly used form of "progestin-only" contraception. Information is limited on the specific P450 isozymes that metabolize MPA; however, it appears that CYP3A4 is 1 pathway of hepatic clearance. Drugs known to be inhibitors of the CYP3A4 pathway (such as protease inhibitors [PIs]) may lead to elevated concentrations of MPA. Secondly, MPA given as DMPA injections has been shown to induce the activity of CYP3A4 by 25 percent. It is possible that this action may result in enhanced clearance of the substrates of CYP3A4, including PIs and nonnucleoside reverse transcriptase inhibitors (NNRTIs), which in turn may result in reduced drug exposure and possible ARV failure. This study is designed to address the lack of information on potential interactions between PIs or NNRTIs and DMPA.